A widely used method of providing certain active properties, e.g., antibacterial, fungistatic or fungicidal properties, to an exposed surface of an object is to cover the exposed surface with a coating composition containing active component(s). The coating composition is applied directly on that surface and then dried on site to form an active coating on the surface. As the majority of the active coating compositions are solvent-based, hazardous volatile organic solvent(s) are evaporated during the application and drying process, which inevitably causes health problems, fire danger, and environmental pollution. Water based active coating compositions need to take a longer time to dry after application, which is less efficient and causes delay of being put into service when needed. All in all, these active coatings are normally thin coatings (e.g., 1-5 mils) that are easily damaged by e.g., abrasion, scrubbing, weathering or wear. Thus, they could only provide limited service life and efficiency to the exposed surface of the object. Further, as these coatings are typically applied thin, there is very little antimicrobial activity per unit area, with resultant lack of microbial protection in high exposure environment.
Some efforts were made to replace active coatings with certain laminates that incorporate active agent(s) to cover the surface of an object. These laminates either use environmental hazardous material(s) as active agent(s), or have various complicated multilayers. The active agents are only added to the laminates at a level so as to protect the covered object itself from microbial degradation. However, these laminates could not provide the desirable antimicrobial efficacy on their exposed surfaces due to the use of the crosslinked polymer systems or extruded thermoplastic polymers to make the laminates. The crosslinked polymer systems or the extruded thermoplastic polymers would lock the active agents in the laminates, thus, hinder the availability of the agents to act on the microbes that are settling on the exposed surfaces of the laminates.
Accordingly, it is desirable for an antimicrobial article in a sheet form that does not include environmentally hazardous material and that has excellent lasting antimicrobial properties for protecting the covered objects from degradation as well as for inhibiting the growth of all types of microorganisms on its exposed surface and being capable of killing these microorganisms. The desirable antimicrobial article in a sheet form should also be easy to make and use.